In the past year, she posted 40 clips of her singing her own songs and cover versions as she accompanied herself on guitar or keyboards.

The last clip was posted five days ago, a cover of David Guetta’s club hit Titanium.

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It includes the lyrics “I’m criticised, but all your bullets ricochet. You shoot me down, but I get up”. On a talent website,

Charleigh had written: “I am very determined. I want to change the world with my music.

“I will never give up trying to achieve my dream. Music is my life, my passion, my dream, my everything. I want to be an inspiration.”

A year ago Charleigh spoke of auditioning for ITV talent show Britain’s Got Talent, and Must Be The Music on Sky1.

The teenager, who celebrated her birthday on Friday, wrote: “I don’t wish to be famous for the money.

"I want to be famous because I want people to relate to music.”

She added that she wanted her songs to be so moving they would make listeners “feel like they’re not alone”.

Friends said Mert had recently finished his A-levels and wanted to take up graphic design.

An amateur film-maker, he and friends made a short movie called Slayer for their final coursework and posted it online last month.

Mert also had a YouTube channel, which showed off his talents behind and in front of the camera.

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British Transport Police is investigating the tragedy but said yesterday officers are not treating the deaths as suspicious.

Supt Phil Wilkinson, from BTP, said: “Our thoughts are with the family and friends of the two teenagers involved in this tragic and acutely sad incident.

“Although my officers are continuing their investigations, as part of our work to prepare a file for the local coroner, there are not thought to be any suspicious circumstances and no one else is believed to have been involved.”

Roger Perkins, a spokesman for First Capital Connect, confirmed that two youngsters were hit by its train.

It was the St Albans to Sutton southbound service, north of the station on the Thameslink route.

Mr Perkins said: “There were no passengers on board the train but there were two drivers in the cab.

"Both are being offered our full care and support.

“We have been giving support to our employees who were at the scene and will do all we can to help the emergency services in their investigation.”

Flowers started to be left yesterday outside Hertswood Academy.

Headteacher Peter Gillett said: “At the start of the school day we were contacted by British Transport Police to inform us of an incident that had occurred overnight involving two of our students.

“As a close community, we are devastated by this tragedy. We are supporting our students and staff in coping with this terrible loss.”